Could that be 3/4". There are box extenders available at your favorite big box store that will solve your problem.

See Link below.

HTH
Chris

Here is a link that might be useful: Box extensions

Use one of these box extenders.

Thank you for the picture. It is worth a thousand words. Now how do you get the socket part up to be level with the new sleeve edge? What if the socket things don't have enough wire to be pulled forward?

By the way...my picture is upside down.

Thanks so much for all the help so far.

taratune,
You have to completely remove the receptacle and re-install it. There had to be enough wire to install it initially, so there ought to be enough even for the extra 3/4".

I don't see any wire wrapped around those screws, so it's most likely back mounted where the wire is inserted into spring-loaded holes. You'll need a small screwdriver to release them. Run those unused screws all the way in before re-installing the receptacle.

1-turn off power
2-remove receptacle
3-install box extender
4-re-install receptacle and faceplate
5-turn on power